Fat Into Bone

Three-quarters of a million Americans had liposuction last year, removing millions of pounds of fat that was simply tossed out, fat that Michael Longaker says could be put to much better use: healing bone.

Previous research shows that certain fat cells can be coaxed to turn into other tissue, including skin, bone, and cartilage. Longaker, a biologist and pediatric craniofacial surgeon at Stanford University Medical Center, figured these multipotent cells—a kind of stem cell—might be useful for treating bone fractures and defects.

To test his idea, he sucked fat cells from the skin of lab mice. He then seeded the cells on a polymer scaffolding, infused them with apatite (a mineral component of bone), and injected the mix into small holes he had drilled into the animals’ skulls. “Eight to 12 weeks later we found we’d been able to heal the defects in the skull that would never have healed naturally in the lifetime of the animal,” Longaker says. “It’s a ‘when in Rome’ type of thing. If the cells get signals from other bone cells, they become bone.”

Longaker and his colleagues want to speed up the process by isolating the fastest bone-growing fat cells. Five to seven years down the road, he predicts, patients recovering from spinal fusion or joint-replacement operations will have some of their own fat cells removed, processed, and implanted at the same time as other surgical procedures. “You could easily obtain enough fat,” he says. “Because the cells are from the patient and the bone is made by them, the body won’t reject it.”